The present invention relates generally to cellulosic fiber composites using protein hydrolysates, and to the method of using protein hydrolysates in the manufacture of agricultural and other cellulosic fiber composites.
Currently, petroleum based binders such as polymeric isocyanates, phenolic and other formaldehyde-based resins, including phenol formaldehyde, phenol resorcinol formaldehyde, and urea formaldehyde, are employed in the manufacture of cellulosic fiber composites such as agfiber board and oriented strand board. However, these binders exhibit several disadvantages such as formaldehyde emissions, high temperature requirements to enable the binders to set, difficulty in handling of resins, and high materials and production costs. It would be desirable to reduce the amount of phenolic and isocyanate resin employed in the production of cellulosic fiber composites.
U.S. Pat. No. 4,944,823 ('823) describes a method for bonding wood surfaces together by heating and pressing using a dry binder formulation constituting a thorough mixture of an isocyanate and a carbohydrate such as a sugar or starch in the manufacture of composite wood products. The sugar or starch replaces a quantity of the isocyanate which would normally have been used, thereby reducing the total quantity of isocyanate. However, the binder described by the '823 patent does not include a source of protein nor protein hydrolysate.
Natural legume-based resins have been employed with cellulosic material in the preparation of rigid, pressure-formed biocomposites (U.S. Pat. Nos. 5,593,625 and 5,635,123). These embodiments employ close to equal amounts of legume-based resin and fiberous cellulosic solids (40-56% resin solids) in the production of fiber-reinforced, protein-based discrete high moisture-content particles having a moisture content of about 55-75% by weight. By assuring that the moisture content remains above 59% by weight, the relatively high amount of legume-based resin fully impregnates the particles such that a new composite material is prepared rather than a material that is produced by gluing fiberous cellulosic solids together by an adhesive. The particles can be combined with a secondary thermosetting binder to form the biocomposite materials. As a result, preparation of such biocomposites requires an additional drying step to reduce the moisture content to less than about 20% by weight prior to pressing.
It would be desirable to produce finished cellulosic fiber composites through a method which employs materials having a relatively low moisture content and which does not require an additional drying stage or step. Therefore, there remains a need for a new fiber-adhesive, resin binder system for use in the manufacture of agricultural and other cellulosic fiber composites, which reduces the amount of phenolic and/or isocyanate resin needed.